Conventionally, in a plasma processing apparatus, a processing target object is mounted on a mounting table which is provided within a chamber. The mounting table is equipped with a conductive edge ring (also referred to as a focus ring) which surrounds the processing target object mounted on the mounting table. As such a focus ring, there is known a focus ring including a first flat portion lower than a mounting surface of the mounting table; and a second flat portion higher than the first flat portion and a processing target surface of the processing target object (see, for example, Patent Document 1). The first flat portion and the second flat portion are formed in sequence from an inner circumferential side of the focus ring toward an outer circumferential side thereof.
Patent Document 1: Japanese Registered Utility Model Publication No. 3,166,974
As, however, processes upon processing target objects are repeated, the focus ring is consumed. If the focus ring is consumed, a shape of the focus ring is changed. Thus, a height relationship between a plasma sheath formed above the focus ring and a plasma sheath formed above the processing target object is also changed. Accordingly, the consumption of the focus ring causes a variation in an incident angle of particles in plasma, such as ions, upon the processing target object.
If a variance in the incident angle of the particles, such as the ions, in the plasma upon the processing target object is increased as a result of the consumption of the focus ring, it is difficult to suppress non-uniformity in an inclination of a hole within a preset range. Thus, the focus ring needs to be replaced before the non-uniformity in the inclination of the hole exceeds the preset range. In case that the focus ring is frequently replaced, however, a process is required to be stopped every time the focus ring is replaced, so that a throughput of the process is reduced.